PXI Registers

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The communication protocol for normal PXI commands is documented below. The size of cmd_buf is calculated from the cmd_hdr. With newer FIRM the total size for command header + buffer must be at most 0x40 words, otherwise Process9 will panic.

Each pxi_id corresponds to a Process9 PXI command-handler(called from threads) which handles the actual command processing. With newer FIRM the pxi_id must be in a certain range.

There's a dedicated Process9 thread for receiving data from PXI(in newer FIRM this is the main-thread), once it finishes receiving a request it copies the cmd_buf into a buffer for the corresponding pxi_id then signals an event so that the cmd-handler thread can process it. Once a cmd-handler thread finishes processing a command, the thread itself then sends the response over PXI. This means that multiple commands for different pxiIDs can be be handled at the same time, even when one cmd-handler completely hangs/etc for example.

Process9 will execute svcBreak when it receives a PXI command with a pxi_id where another cmmand with that same pxi_id is still being processed by the command-handler(this won't happen with commands sent by the ARM11 PXI-module, since it waits for the command reply before sending another command request for that same pxi_id).


A11->A9 (u32) pxi_id
A11->A9 (u32) cmd_hdr
A11->A9 (u32[]) cmd_buf


A9->A11 (u32) pxi_id
A9->A11 (u32) cmd_hdr
A9->A11 (u32[]) cmd_buf


0 = pxi_mc
1 = pxi_fs
2 = pxi_fs
3 = pxi_fs
4 = pxi_fs
5 = pxi_pm
6 = pxi_dev
7 = pxi_am
8 = pxi_ps
9 = stubbed


Old3DS Name Address Width Used by
Yes PXI_SYNC9 0x10008000 4
Yes PXI_????9 0x10008003 1
Yes PXI_CNT9 0x10008004 4
Yes PXI_SEND9 0x10008008 4
Yes PXI_RECV9 0x1000800C 4
Yes PXI_SYNC11 0x10163000 4
Yes PXI_CNT11 0x10163004 4
Yes PXI_SEND11 0x10163008 4
Yes PXI_RECV_11 0x1016300C 4

The PXI registers are similar to those on DS.


Bit RW Description
0-8 R Data input from bit8-15 of PXI_SYNC11
8-15 R/W Data output to bit0-8 of PXI_SYNC11
23 ? ?
29 ? ?
31 ? ?


Bit RW Description
0 R Send Fifo Empty Status (0=Not Empty, 1=Empty)
1 R Send Fifo Full Status (0=Not Full, 1=Full)
2 R/W Send Fifo Empty IRQ (0=Disable, 1=Enable)
3 W Send Fifo Clear (0=Nothing, 1=Flush Send Fifo)
8 R Receive Fifo Empty (0=Not Empty, 1=Empty)
9 R Receive Fifo Full (0=Not Full, 1=Full)
10 R/W Receive Fifo Not Empty IRQ (0=Disable, 1=Enable)
14 R/W Error, Read Empty/Send Full (0=No Error, 1=Error/Acknowledge)
15 R/W Enable Send/Receive Fifo (0=Disable, 1=Enable)